From the existing research, many scholars ignore the phenomenon of imperfect maintenance in the process of equipment maintenance. In this paper, a model of component's state degradation and imperfect maintenance is established by Gamma process. With the goal of minimizing the cost per unit life cycle as the optimization objective and the component combination maintenance as the basic strategy, an optimal decision-making model of the multi-component system based on the maintenance threshold is established. Based on Monte Carlo method, the optimal visual maintenance strategy of multi-component system is obtained through a lot of simulation analyses. The results of the case study show that the optimal model of Condition-Based Maintenance(CBM) strategy can significantly reduce the maintenance cost and improve the system availability.